Projectors are known that use a solid-state light source such as an LED (Light Emitting Diode) as a light source of each of colors, red, green and blue. With these projectors, modulated light (image light), which is light from the solid-state light source of each color which has been spatially modulated, is projected on a screen to thereby display a color image.
Generally, the luminance (the amount of light) of a solid-state light source changes depending on the installation environment (particularly, the temperature), the changes over time in materials, and so on, but the degree of change in the luminance is different for the solid-state light source of each color. Thus, with the projectors described above, the luminance balance of the solid-state light source of each color changes depending on the installation environment, the changes over time in the materials for the solid-state light source, and so on, and as a result, the tone (white balance) of a white image (white light) projected on a screen is changed.
Patent Document 1 describes a light amount control device that is capable of providing an optimal white balance by adjusting the amount of light of an LED of each color of a projector including a plurality of LEDs that emit light different colors.
The projector described in Patent Document 1 includes a group of a plurality of red LEDs, a group of a plurality of green LEDs, and a group of a plurality of blue LEDs, and a driving current based on a set value is supplied to each group. The driving current is supplied in turn for each group.
The light amount control device includes one light detection element for detecting light output from the LED of each color, sampling means for acquiring light intensity of each group by sampling output from the light detection element in synchronization with supplying a driving current for each group, and feedback means for changing a set value of each group in such a way that the acquired light intensity of each group is at the reference value set for each group.
According to the light amount control device described above, the light intensity of each group is adjusted to be at the reference value set for each group, and thus, the tone (the white balance) of white light obtained by combining the light from the LEDs of respective groups can be maintained at an optimal value.